Flash Sintering of Multiphase Ceramics

传统上，从陶瓷粉或粘土制造部件的过程需要在高温下在炉子中长时间(数小时或数天)烧成(烧结)，这是一个耗费大量能源的昂贵过程。一种名为“闪速烧结法”的新工艺需要电流直接流过陶瓷块，使陶瓷致密化，并在几秒钟内生产出可用的部件。最初的研究表明，许多类型的陶瓷都可以用这种方法烧制，但这些研究主要集中在单相材料上，而实际应用往往需要由不同类型的陶瓷组成的多相陶瓷。该奖项支持基础研究，以调查多相陶瓷的每个组分的电和热行为如何响应闪速烧结。这项工作将导致对闪速烧结工艺的新理解，这将使这些关键材料的加工和制造成本更低、效率更高。将研究这些材料的加工和强度，以确保用这种新工艺制造的部件与传统方法制造的部件相媲美或更好。该项目的科学成果被整合到视频模块中，用于向中小学生推广，以展示科学家和工程师正在研究在制造新材料的同时节约能源的方法。为了提高机械强度、提高导热系数和提高抗热震性，陶瓷构件通常需要多相。与传统的烧结方法不同，传统的烧结方法需要大量的能量来加热样品和炉腔，而高外加电场和流经样品的电流可以在空气中使用，而不需要施加压力和更低的温度来致密氧化物陶瓷。这项研究计划将评估如何使用电场的直接应用来闪速烧结多相陶瓷粉末压坯。具有不同电性/离子电导率和热导率的多组分氧化物系统被用来确定这些材料性能在促进闪速烧结中的作用。这些信息被用来创建成分设计参数，以通过加入次要相来优化闪速烧结。将闪速烧结复相陶瓷复合材料的力学性能与传统烧结材料进行了比较，以评价其差异，并用电子显微镜对其微观结构进行了表征。

Traditionally, the process to make a components from ceramic powders or clays requires firing (sintering) in a furnace at high temperatures for a long time (many hours or days), a costly process that consumes a large amount of energy. A new process known as "flash sintering" involves running electrical current directly through the piece, to densify the ceramic and produce a usable component in a matter of seconds. Initial studies show that many types of ceramics can be fired this way, but these studies have focused on single phase materials, while practical applications often require multiple phases made of different types of ceramics. This award supports fundamental research to investigate how the electrical and thermal behavior of each component of a multi-phase ceramic responds to flash sintering. This work will lead to new understanding of the flash sintering process, which will allow for lower cost, higher efficiency processing and manufacture of these critical materials. The processing and the strength of these materials will be studied, to ensure that the components made by this new process are comparable to or better than those made by traditional methods. The scientific results of the project are integrated into video modules for outreach to elementary and middle school children, to demonstrate the ways that scientists and engineers are studying methods to save energy while making new materials. Multiple phases are often required for ceramic components in order to improve mechanical strength, enhance thermal conductivity, and increase thermal shock resistance. In contrast to conventional sintering approaches which expend significant energy heating the sample and furnace cavity, a high applied electric field with current flowing through the sample can be used to densify oxide ceramics in air and without applied pressure and at much lower temperatures. This research program will evaluate how the direct application of electric fields can be used to flash sinter multiphase ceramic powder compacts. Multicomponent oxide systems with phases of varying electrical/ionic and thermal conductivity are used to determine the role of these material properties in promoting flash sintering. This information is used to create compositional design parameters to optimize flash sintering via incorporation of minor phases. Mechanical properties of flash sintered multiphase ceramic composites are compared to conventional sintered materials to evaluate any differences, with microstructural characterization by electron microscopy.